Correlation Based Filter

Question

i found this paper. Im interesting in part 2.3 Feature Weighting. The correlation function is known from wikipedia and almoast clear ( i can write a function to calculate the value :) )

But now i want to generate sutch a feature set. But i cant understand the formula. What is this

H(X)?

I think

IG(X|Y) is the correlation between X and Y

Could you give me help to write this function ? - Or the read the paper

Answer 1

$H(X)$ is the entropy of $X$, $H(X|Y)$ is the conditional entropy, and $IG(X|Y)$ is the mutual information. Have a look at http://en.wikipedia.org/wiki/Mutual_information for a basic introduction.